Method of collimating fibers

ABSTRACT

A method for collimating a plurality of filaments into parallel, side-by-side contiguous relation including passing the filaments around first and second rollers, the rollers having their axes perpendicular to, but noncoplanar with, each other whereby all but one filament will be subjected to sidewise forces.

United States Patent Malcolm Basche West Hartford;

Urban E. Kuntz. East Hartford, both 01, Conn.

Jim. 19, 106') Aug. 31. 1971 United Alt-craft Corporation East Hartlord,Conn.

Inventors Appl Nu, llled Patented Asslgnee METHOD OF COLLlMATlNG FIBERSl Chim,3Draw1ng Figs.

U.S.Cl 226/196, 19/65 T, 156/161, 156/181 Int. Cl ..B65h-23/26,

DOlh 13/02, B65h57/14 FieldofSearch 156/181,

Relerences Clted UNITED STATES PATENTS Schmidt Smith Smith Remr TarbellGallagher.... Balch et a1.

FOREIGN PATENTS Great Britain Primary Examiner-Carl D. QuarforthAssistant Examiner-Roger S. Gaither Attorney-John D. Del Ponti 226/196 X19/65 '1 19/65 T l9/66T 19/65 T ABSTRACT: A method for collimating aplurality of filaments into parallel, side-by-side contiguous relationincluding passing the filaments around first and second rollers, therollers having their axes perpendicular to, but noncoplanar with, eachother whereby all but one filament will be subjected to sidewise forces.

PATENTED was] IBYi 3,602,416

SHEET 1 [IF 2 INVENTORS MALCOLM BASCHE URBAN E. KUNTZ ATTORNEY PATENTEUM1831 \sn 3.602.416

SHEEI 2 0r 2 F/GJ METHOD OF COLLIMATING FIBERS BACKGROUND OF THEINVENTION 5 This invention relates to the production of multiple fibercomposite tape and more particularly relates to means for collimating aplurality of individual filaments into a parallel sideby-siderelationship to facilitate the production of unidirectionalfiber-reinforced composites.

It is known that fiber strengthening offers the potential of significantimprovements in the fabrication of composite materials. The concept offiber strengthening is based on the fact that materials produced infibrous form frequently exhibit a higher elastic modulus and a higherstrength than the corresponding materials in bulk. In order to exploitthe attractive physical properties of continuous filamentary materialshowever, it is necessary to gather the fibers together into a compositestructure in such a way that failure in several isolated fibers will notbe transmitted to .the surrounding fibers and further, to distribute theload with reasonable uniformity over the entire fiber bundle. One methodof achieving this result is to gather the fibers into a collimatedrelationship and infiltrate them with matrix material to form amonolayer tape.

One of the paramount problems in continuously producing unidirectionallyreinforced composite tapes resides in the inherent difficulty ofincorporating the fibers into the matrix material. There are basicallytwo ways in which continuous filaments may be incorporated into thematrix in a parallel, uniformly spaced fashion. One way is to precisionalign the filaments in noncontacting relation prior to encasement and tocontrol their spacing by tension means until the matrix material isapplied. Because of the elaborate and intricate equipment necessary tomaintain exact spacing, this procedure is unsatisfactory and isgenerally considered commercially unattractive. The other general methodinvolves precoating each individual filament with matrix material sothat the fibers can subsequently be aligned in side-by-side contactingrelation with the filaments being spaced apart by the thickness of thecoatings. Although this procedure has done away with the problem ofspacing maintenance it has generated new problems, one of which is theassiduous requirement that the apparatus be capable of causing theindividual, precoated filaments to continuously assume and maintainintimate side-byside contact in a monoplanar configuration. The priorart has shown apparatus for collimating filaments together into aribbon, however, these prior techniques incorporate specializedcomponents, often unreliable, as for example concave roller or toothedcomb elements in order to achieve the aforesaid collimation.

Exemplary of the prior art teachings are those shown in Letters PatentU.S. Pat. No. 3,009,5[2 issued to Guay on Nov. 2|, I961 and US. Pat. No.3,258,378 issued to Kelsey on June 28, I966. The Guay patent teaches theuse of a concave highly polished roll across which a plurality offilaments are pulled under tension in order that the filaments will cometogether under the influence of a sidewise pressure. Unfortunately, theoperation of the Guay device frequently resulted in the filaments ridingone over the other. One of the disadvantages of the Guay device can betraced to the use therein of a collimating roller with a nonconstantdiameter so that adjacent fibers, in passing thereover, are subjected todifferent circumferential speeds and hence imbalances in filamenttension and sidewise pressure effects. The Kelsey patent, in an effortto resolve the problems of the Guay device, taught that a tiltable combcould be utilized. in conjunction with a tension inducing roller pair,to position the filaments adjacent to each other without the generationof any sideways pressure at all. The Kelsey teaching requires that thetoothed comb be maintained at a precise inclination so that the cosineof the angle of tilt of the comb multiplied by the spacing of thethreads be equal to the widths of the threads. To this end, amicrometric screw adjustment was provided.

The present invention. while utilizing some of the concepts underlyingboth the Guay and the Kelsey processes, produces monolayer tapes by adistinct and different process and by an improved and simplifiedapparatus without the necessityfor concave rollers, adjustable toothedcombs or any other specializedequipment at all. I

SUMMARY OF THE INVENTION 2 I The present invention relates to a meansfor collimating a plurality of filaments into a parallelside-by-s'iderelationship preparatory to integration into monolayer tapeproduct without necessitating the use of concave roller or toothed combelements. The technique includes an improved process and' apparatuswhereby adjacent filaments initiating from diverse sources areautomatically made to assume a continuous contacting relation by theexertion of a sidewise pressure induced by the juxtaposed relation of asequence of rollers.

According to one aspect of this invention, a plurality of continuousfilaments each issuing from a separate feed source are sequentiallypassed around a pair of cylindrical rollers, the rollers being solocated with respect to each other that the filaments issuing from thefirst roller are subjected to sidewise forces and are naturally made toassume an intimate state of contact whereby high quality is assuredwithout the necessity for critical production control. One advantageousfeature of the present apparatus is the fact that substantially allcontact with the fibers during the orientation period is a rollingcontact so that the likelihood of wear and damage to both the fiber andthe equipment is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective viewof typical apparatus used in the practice of the invention;

FIG. 2 is a plan view of a portion of the apparatus shown in FIG. I; and

FIG. 3 is a plan view of the rollers shown in FIG. 2 but with their axesin a nonperpendicular orientation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,wherein like numbers indicate like elements, a series of supply rolls orspools 10 are provided as a convenient source of filaments 12. Thefilaments l2 assume a rolling contact with a pair of cylindrical rollers14 and 16 and pass therearound as shown. The roller 14 acts as a spacingidler or guide roller while the roller I6 acts as a collimating rollerwhen the rollers are critically disposed in a particular angularrelationship, as hereinafter described, so that the filaments areinduced to issue from the roller 16 as a monolayer of contiguous andcoplanar collimated fibers. The fibers are subsequently transfixed intopermanently collimated relation by means of a matrix overcoat applied bypassage through a resin pot I8 and curing furnace 20. A detailed exampleof a practical coating apparatus is described in copending applicationSer. No. 752,080 entitled Process for Coating Filaments with a Resin andApparatus Therefor" filed Aug. 12, 1968 and sharing a common assigneewith the instant invention. After coating and curing, the resultingunidirectional fiber reinforced tape is passed over a guide roller 22and stored on a takeup reel 24.

The spools 10 are preferably arranged in banks with each bank of spoolshaving the spools positioned with their axes parallel but at staggeredelevations as shown in the drawings. However, it will be appreciatedthat so long as the spools 10 are sufficiently staggered to preventfilament interference, they may be arranged in any practicalconfiguration. The number of supply spools utilized is a matter ofchoice with an upper quantity limit being determined by the axial lengthof the rollers 14 and 16.

As hereinbefore suggested, the angular relation of the idler l4 and thecollimating roller 16 is precise and crucial. The two rollers must bedisposed so that a sidewise pressure will be exerted on all but one ofthe filaments. In particular, the rollers must be disposed with theiraxes perpendicular to each other. Such a relationship assures that allof the filaments 12 will automatically be made to assume side-by-sidecontact on the collimating roller 16. It will be appreciated that one ofthe advantages of the instant invention is that if one of the filamentsbreaks during the operation, the remaining fibers will seek intimacy andclose the gap created thereby, thus salvaging what would otherwise beunacceptable tape. That two common rollers could produce such dramaticresults in terms of collimating efficiency was a discovery totallyunexpected, particularly in view of the prior art techniques. Thediscovery is best explained with reference to FIG. 2 wherein is shownthe two rollers positioned with their axes mutually perpendicular butnot coplanar. Because of this roller relationship, only one of thefilaments, designated by the numeral 12', can make an angle of 90 withthe axis of the collimating roller 16. All of the other filaments 12"make angles which are either less than or greater than 90. As thefilaments are pulled over the collimator l6 and cause it to rotate, apoint P representing the point of initial contact between the roller andthe filament 12" is caused to move. As the roller rotates, the point Pon the roller moves to P while the corresponding point P on the filamentmoves to P". There is thus a relative axial slip P'-P" which, sincethere is friction between the filament and the roller, will cause asidewise force to act on each filament 12" tending to displace themtowards the base fiber 12'. As the filaments come together into amonolayer of parallel fibers, the sidewise forces will diminish but willnevertheless act to maintain the fibers in abutting contact since thefilament diameter, while small, is still finite and all but the basefilament will have an angle with the axis of roller by which it differsslightly from 90. As can be seen from the foregoing, one of theadvantages inherent in the system resides in the fact that the automaticdiminution of sliding contact between fiber and roller acts as asafeguard to keep the fibers from riding up over one another.

In contrast to the aforesaid concept and, as can be seen in FIG. 3, whenthe axes of rollers 14 and 16 are not mutually perpendicular, thereexists a situation where more than one filament can be simultaneouslyperpendicular to the axis of the roller 16. As a result, the filamentswill not seek intimacy with each other and will instead be spaced apartby an exact amount dependent upon the departure from mutualperpendicularity of the rollers 14 and 16. It is only when the rollersare disposed in the critical relation as heretofore described that allof the filaments will assume, in a monolayer, a continuously contactingcollimated relation.

in one investigation with the apparatus as shown in FIG. 1, l0 fibers of4 mil boron filament precoa'ted with a 0.2-0.4 mil coating of polyimideresin were passed through a rod-sealed mercury wipe resin pot at a speedof 400-800 ft./hour. The precoated boron filaments assumed a contiguouscollimated relation with no spacing detectable therebetween so thatafter the application of the resin overcoat, the resulting tapedisplayed fibers that were evenly and uniformly spaced with no boron toboron contact. The tape was tested and had a tensile strength of 198,000p.s.i. and a 36x10? p.s.i. modulus.

While for the sake of clarity and brevity, the foregoing description hasbeen made with respect to specific examples, processes and parameters,these specific embodiments will be understood to be illustrative only,and no limitation is intended thereby. It should for example beunderstood that the instant method and apparatus for collimating fibersis applica ble to all kinds of filaments whether or not precoated.Various other modifications and alternatives will be evident to thoseskilled in the art within the true spirit and scope of the invention asset forth in the appended claims.

What is claimed is:

l. A method of collimating a plurality of continuous filaments intoparallel side-by-side contiguous relationship which comprises,

providing first and second cylindrical rollers with the axis of oneroller perpendicular to, but not coplanar, with the axis of the otherroller, supplying a plurality of at least three individual andnoncontiguous filaments to be guided around each roller under tension,

passing the tensioned filaments around the first roller in a generallyparallel, side-by-side relationship such that no one tensioned filamentoverlays any other tensioned filament when passing around the firstroller,

extending the tensioned filaments towards said second roller wherebyonly one of the filaments extending from said first roller to saidsecond roller will be perpendicular to the axis of the second roller andthe remaining extended filaments on either side of said one filamentwill be urged towards a relationship with the axis of the second roller,

and further passing the extended filaments around the second roller toform a monolayer of parallel filaments.

1. A method of collimating a plurality of continuous filaments intoparallel side-by-side contiguous relationship which comprises, providingfirst and second cylindrical rollers with the axis of one rollerperpendicular to, but not coplanar, with the axis of the other roller,supplying a plurality of at least three individual and noncontiguousfilaments to be guided around each roller under tension, passing thetensioned filaments around the first roller in a generally parallel,side-by-side relationship such that no one tensioned filament overlaysany other tensioned filament when passing around the first roller,extending the tensioned filaments towards said second roller wherebyonly one of the filaments extending from said first roller to saidsecond roller will be perpendicular to the axis of the second roller andthe remaining extended filaments on either side of said one filamentwill be urged towards a 90* relationship with the axis of the secondroller, and further passing the extended filaments around the secondroller to form a monolayer of parallel filaments.